In many optical telecommunication networks, such as wavelength-division multiplexing (WDM) networks, one transmission fiber can support a plurality of channels. These channels are subject to loss in the optical network, which includes loss from the transmission fiber. Optical amplifiers (OAs) are often implemented to compensate for this loss. However, the gain experienced in the OAs can vary for different channels. In response, equalizers are employed to optimize the power of each channel before transmission, which pre-adjusts for the varied gain experienced by different channels.
Although this method may be acceptable in steady-state conditions, problems arise when the network is reconfigured and the number of channels being amplified by an OA changes. The number of channels refers to how many channels are actually present at a given instant, as opposed to channels that have negligible power. The gain experienced by each channel being amplified by an OA is dependent on the other channels being amplified by the OA at the same time. Therefore, when the network is reconfigured and the number of channels being amplified by an OA changes, the gain for other channels being amplified by the OA will also change. This may lead to undesirable power excursion for the other channels, which reduces the network's performance. The equalizer must then be re-optimized to account for the new gain values for each channel.
Currently, optical networks rely on real-time measurement of the gain/loss experienced by each channel following network reconfiguration to re-optimize the channel power, which can often be a lengthy process. In addition, to avoid a large power excursion for the existing channels after the network is reconfigured but before the channel power is re-optimized, the number of channels is changed in small increments. This precaution further increases the time it takes to reconfigure the network. As such, there exists a need for quick and practical methods to reconfigure a network without causing a large power excursion in the existing channels.